What do the laws of thermodynamics look like, when applied to
microscopic systems such as optically trapped colloids, single molecules
manipulated with laser tweezers, and biomolecular machines? Over the past decade
or so there has been considerable interest and progress in addressing this
question. I will give an overview of some of these developments, with a focus on
results pertaining to fluctuations far from thermal equilibrium, and I will
argue that these developments have refined our understanding of the second law
of thermodynamics.